A known deflector (roof spoiler) arranged at a roar of a roof panel and an upper of a rear window of a vehicle and extended in a vehicle width direction is disclosed in JPH10-24869A (hereinafter referred to as Patent reference 1). According to Patent reference 1, a position, or attitude (an angle) of the deflector is changed in accordance with weather. When it rains, the position, or attitude of the deflector is controlled so that an upper surface of the deflector is positioned horizontally, and substantially planar with an upper surface of the roof panel. In a state where the upper surface of the deflector is positioned horizontally, and substantially planar with the upper surface of the roof panel, a clearance is formed between the deflector and the upper of the rear window and a part of air flowing from front to rear of the vehicle along the upper surface of the roof panel flows along the rear window via the clearance. Accordingly, the adhesion of the dirt, for example, rain, mud and dust to the rear window may be reduced. On the other hand, according to Patent reference 1, when it is fine weather, a front end portion of the deflector is substantially planar with the upper surface of the roof panel and the position, or attitude of the deflector is controlled so that a rear end portion of the upper surface of the deflector is positioned lower than the front end portion of the upper surface of the deflector. In a state where the rear end portion of the upper surface of the deflector is positioned lower than the front end portion of the upper surface of the deflector, the clearance is closed and air flowing from the front to the rear of the vehicle along the upper surface of the roof panel is introduced to the rear of the vehicle without flowing toward the rear window. According to Patent reference 1, as the rear end portion of the upper surface of the deflector is positioned lower than the front end portion of the upper surface of the deflector, air passing over the roof panel flows obliquely downward along the upper surface of the deflector. Thus, a negative pressure area at the rear of the vehicle is narrowed, resulting in that air resistance is reduced. Accordingly, fuel efficiency is improved.
According to Patent reference 1, the deflector is configured not to be protruded higher than the upper surface of the roof panel in order to reduce air resistance in rainy weather and fine weather as much as possible. Thus, when air flows from the front to the rear of the vehicle along the upper surface of the roof panel in rainy weather, an amount of air flowing along the rear window via the clearance is small. Particularly when the vehicle runs at a low speed, the amount of air flowing along the rear window is very small. Accordingly, the adhesion of the dirt to the rear window may be reduced sufficiently.
A need thus exists for a deflector apparatus which is not susceptible to the drawback mentioned above.